PITTSBURGH (AP)  A third former teacher from Plum High School in western Pennsylvania was sentenced Wednesday to three to six years in prison for sex crimes involving a female student, prompting the judge to refer to the school as a “cesspool.”

Michael Cinefra, 30, of Verona, pleaded guilty in November to involuntary deviate sexual intercourse, institutional sexual assault and other charges involving a 15-year-old girl. He surrendered his teaching license and also is to spend 10 years on probation after his prison term.

“It was the biggest mistake of my life,” Cinefra told the judge.

Ex-teachers Joseph Ruggieri and Jason Cooper have already begun serving prison sentences after pleading guilty to sex crimes involving students over 16. Sixteen is the legal age of sexual consent in Pennsylvania except in such instances as teacher-student relationships.

Allegheny County Judge David Cashman on Wednesday denounced the school as a “cesspool” and said, “I didn”t like the plea agreement in the first case. I didn”t like the plea agreement in the second case. I don”t like the plea agreement in the third case.”

Cashman said that “given my druthers, these three would be looking at decades (in prison),” the Pittsburgh Post-Gazette reported.

But the judge also noted that the guilty pleas spared the victims from testifying at trial.

A grand jury convened by Allegheny County District Attorney Stephen Zappala Jr. investigated whether the school principal, the district superintendent and others did enough to investigate and report allegations of teacher-student relationships years before the three teachers were charged.

In a May report, the grand jury noted changes in state law since the Penn State-Jerry Sandusky child sex abuse scandal. The panel said Plum school officials may not have broken the law by failing to report rumors of teacher-student relationships under old standards, but may have been prosecuted had the more stringent, post-Sandusky standards been in place at the time.

The school is about 15 miles east of Pittsburgh.

Cinefra was 25 when he gave the girl alcohol and repeatedly had her perform a sex act on him in 2011.

“He let himself down, his family, his profession and the school district,” defense attorney Patrick Thomassey said. “He”s ruined his life. He knows it.”

Ruggieri, 42, is serving two to five years in prison; Cooper, 40, is serving 1½ to 3 years.

A fourth Plum teacher charged in the scandal was acquitted last year. Drew Zoldak was not accused of having sex with students. He was accused of trying to intimidate Ruggieri”s victim by pointing her out in class in April 2015, but a jury found him not guilty.